Cylinders in diesel engines create high temperatures which are transmitted to the head gaskets that are employed for sealing between the cylinder and the cylinder head and which also seal coolant passages in the cylinder and cylinder head. In some forms of head gaskets now in use, as for example the gasket disclosed in U.S. Pat. No. 3,448,986, the gasket includes a thin metal plate having a central opening communicating with the interior of the cylinder, a series of circumferentially spaced openings for registration with the coolant passages, and with a sealing member of resilient material mounted in the latter openings and in sealing contact with the cylinder and cylinder head. Because it is undesirable to transmit high heat from the cylinder to the resilient sealing members, the metal portion of the gasket has a thickened portion immediately surrounding the central opening and which is sealingly clamped between the cylinder and cylinder head. The remaining portion of the metal plate is thinner so that it will be substantially out of contact with the opposed faces of the cylinder and cylinder head and therefore carry less heat from the thickened portion to the resilient sealing member.
In recent years diesel engines of increased horsepower have been developed and which produce higher temperatures within the cylinder than formerly. This requires that additional means be provided for preventing excess heat from being transmitted to the resilient sealing members.